1. Field of the Invention
The present invention generally relates to chip antennas, and more particularly, to a broadband chip antenna for use in wireless communication networks and equipment, including short-distance wireless communication and personal mobile communication networks and equipment.
2. Description of the Related Art
When developing and designing wireless mobile communication devices, due to the constraint on size, monopole antennas 10 with a quarter wavelength, as shown in FIG. 1, are generally incorporated in device as basic units. However, the developing direction is moving slowly toward devices that are lighter, thinner, shorter, and smaller.
The concept of using a special winding shape to shorten the length of a wire antenna is first developed in 1984. For instance, a winding antenna of a zigzagging or meandering shape is disclosed by H. Nakano, H. Tagami, A. Yoshizawa, and J. Yamauchi in an article entitled xe2x80x9cShortening Ratios of Modified Dipole Antennaxe2x80x9d, which is published in IEEE Trans. Antennas Propagat., AP-32, pp. 385-386. In 1996, a winding antenna of a bow-tie shape, which further shortens the antenna length, is disclosed in xe2x80x9cIEEE AP-S International Symposiumxe2x80x9d, pp. 1566-1569 by M. Ali and S. S. Stuchly.
FIG. 2 shows a conventional chip antenna 20 of a meandering type (European patent 0 764 999 A1). The chip antenna 20 has a substrate 22 of a dielectric and/or magnetic material. A metal conductor 24 is disposed in or on the outer surface of the substrate as a meandering line, or a zigzagging line (not shown). One end of the metal conductor 24 is used as a feeding point 26, which is connected to the feeding pad 28. By utilizing the intrinsic characteristic, length, and number of turns or curves of the metal conductor, the general design principle regarding self-matching functions can be achieved so that the antenna can have proper resonance and radiation. However, one drawback of this type of chip antenna is that it has limited range on reduction of size.
As shown in FIG. 3, another type of conventional chip antenna 30 (U.S. Pat. No. 5,764,198) uses a spirally wounding conductor 32 and a capacitor 34 connected in parallel to achieve the matching function for the antenna. Although the chip antenna of this type is of a reduced size, its bandwidth is limited.
Due to the difficulty in bandwidth expansion for the above-discussed chip antenna, it is a primary object of the present invention to provide a chip antenna having a substrate, feeding pad, feeding conductor, matching unit, and meandering conductor to effectively expand bandwidth and reduce size.
The above and other objects, which will become apparent in reading the specification below, are realized by a chip antenna that has a substrate of a dielectric material and one or more layers, and a feeding pad formed on an outer surface of the substrate for signal injection. In particular, a meandering conductor is disposed on at least one layer of the substrate for use as a radiator unit. A conductor is disposed on a substrate layer for use as a feeding conductor for the antenna, and for propagating signals when connected to a signal source. A matching unit disposed on the layers of substrate includes a matching conductor and a ground in which the matching conductor is shielded by at least one plate of the ground. In particular, portions of the matching conductor are respectively connected to the meandering conductor, ground, and feeding conductor.
Other objects and the features will be apparent from the following detailed description of the invention with reference to the appended drawings.